IN Brief:
- Fraunhofer IKTS is developing a membrane reactor for climate-neutral lime production.
- The Green Lime project captures process CO2 from lime burning and converts it into methane, hydrogen, and elemental carbon.
- The technology targets one of the hardest parts of construction material decarbonisation: emissions released directly from mineral processing.
Fraunhofer IKTS is developing a membrane reactor designed to enable climate-neutral lime production for the construction materials industry.
The work is being carried out at the Fraunhofer Institute for Ceramic Technologies and Systems in Hermsdorf, Thuringia, as part of the Green Lime project. The process captures carbon dioxide released during lime calcination and uses it as a raw material rather than venting it to the atmosphere.
Lime is used in cement, plaster, mortar, and other construction products, but its production is highly emissions-intensive. The issue is not only the fuel used to heat kilns. Carbon dioxide is also released from the raw material itself when limestone is burned, making simple fuel switching insufficient for full decarbonisation.
Fraunhofer IKTS is addressing that process-emissions problem by combining a specially developed membrane reactor with a sealed electric furnace. Carbon dioxide released from the lime is captured and reacted with green hydrogen to produce methane. The methane is then pyrolysed into hydrogen and elemental carbon, also known as carbon black.
The hydrogen can be recirculated back into the plant, while the elemental carbon may be used in other industrial or agricultural applications. Fraunhofer IKTS said the system draws on its expertise in materials development, plant design, and system integration, with possible applications beyond lime production, including waste management and cement.
Mineral-based construction materials sit at the centre of the built environment’s carbon challenge. Cement, lime, aggregates, ceramics, glass, and mineral coatings depend on high-temperature processes and chemical transformations that are difficult to decarbonise fully. Electrification can reduce fuel emissions, but it cannot remove process carbon where the chemistry of the material releases CO2.
That distinction is important for specifiers and construction clients. Much of the industry’s carbon reduction work has focused on operational energy, recycled content, cement substitution, efficient logistics, and lower-carbon concrete mixes. Those measures remain important, although process emissions require more fundamental industrial technology changes at the manufacturing stage.
Lime also occupies a complex position in the materials supply chain. It is used directly in construction and indirectly through cement and other mineral products. Any viable decarbonisation route therefore affects plaster manufacturers, mortar producers, cement works, coatings suppliers, and contractors working under lower-carbon procurement requirements.
Carbon capture and utilisation is commercially attractive where it treats carbon dioxide as a feedstock rather than a waste stream. Its wider use will depend on energy input, hydrogen supply, product quality, plant integration, and regulatory recognition. The economics of the process will also depend on whether the recovered carbon and hydrogen streams can be used reliably and whether the system can operate at industrial scale.
Policy treatment remains a practical question. Long-term carbon storage is increasingly recognised within industrial decarbonisation strategies, while carbon utilisation can be harder to account for if the captured carbon later re-enters the atmosphere. For construction materials, the strongest case will come where carbon is locked into durable products or where the process materially reduces primary emissions without creating new supply risks.
The Green Lime project is not yet a mainstream product specification. Its relevance lies in the type of problem it addresses: unavoidable process emissions from materials that remain central to modern building. As clients demand lower embodied carbon across buildings and infrastructure, pressure will move upstream from contractors to manufacturers.
Technologies such as Fraunhofer IKTS’s membrane reactor show where that pressure may lead. Future material production systems are likely to combine electrification, hydrogen, carbon capture, and circular raw material recovery, with construction clients demanding evidence that those changes are reflected in the products they specify.
